U.S. patent application number 15/546004 was filed with the patent office on 2018-01-04 for crystal resonator plate and crystal resonator device.
This patent application is currently assigned to Daishinku Corporation. The applicant listed for this patent is Daishinku Corporation. Invention is credited to Takuya KOJO.
Application Number | 20180006630 15/546004 |
Document ID | / |
Family ID | 56542820 |
Filed Date | 2018-01-04 |
United States Patent
Application |
20180006630 |
Kind Code |
A1 |
KOJO; Takuya |
January 4, 2018 |
CRYSTAL RESONATOR PLATE AND CRYSTAL RESONATOR DEVICE
Abstract
An AT-cut crystal resonator plate (2) includes a first main
surface (2a) on which a first excitation electrode (211) is formed
and a second main surface (2b) on which a second excitation
electrode (212) is formed. The AT-cut crystal resonator plate (2)
further includes: a substantially rectangular-shaped vibrating part
(21) that is piezoelectrically vibrated when a voltage is applied
to the first excitation electrode (211) and the second excitation
electrode (212); a holding part (22) protruding from a corner part
(21a) of the vibrating part (21) in a Z' axis direction of the
AT-cut crystal; and an external frame part (23) configured to
surround an external circumference of the vibrating part (21) and
to hold the holding part (22).
Inventors: |
KOJO; Takuya; (Kakogawa-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Daishinku Corporation |
Kakogawa-shi, Hyogo |
|
JP |
|
|
Assignee: |
Daishinku Corporation
Kakogawa-shi, Hyogo
JP
|
Family ID: |
56542820 |
Appl. No.: |
15/546004 |
Filed: |
October 30, 2015 |
PCT Filed: |
October 30, 2015 |
PCT NO: |
PCT/JP2015/080667 |
371 Date: |
July 24, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H03H 9/17 20130101; H03H
9/02 20130101; H03H 9/0595 20130101; H03H 9/19 20130101 |
International
Class: |
H03H 9/05 20060101
H03H009/05; H03H 9/17 20060101 H03H009/17 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 29, 2015 |
JP |
2015-015784 |
Claims
1. An AT-cut crystal resonator plate including a first main surface
on which a first excitation electrode is formed and a second main
surface on which a second excitation electrode is formed,
comprising: a substantially rectangular-shaped vibrating part
having the first excitation electrode and the second excitation
electrode; a holding part protruding from a corner part of the
vibrating part in a Z' axis direction of the AT-cut crystal so as
to hold the vibrating part; and an external frame part configured
to surround an external circumference of the vibrating part and to
hold the holding part.
2. The crystal resonator plate according to claim 1, wherein the
first excitation electrode and the second excitation electrode are
each formed at a position spaced apart from a region on an extended
line of the holding part in the Z' axis direction toward a central
direction of the vibrating part.
3. The crystal resonator plate according to claim 1, wherein the
holding part is protruded toward the external frame part from each
of two corner parts disposed in the vibrating part in the Z' axis
direction.
4. The crystal resonator plate according to claim 1, wherein the
holding part is protruded toward the external frame part from one
corner part disposed in the vibrating part.
5. The crystal resonator plate according to claim 1, wherein the
external frame part has a thickness larger than a thickness of the
holding part.
6. The crystal resonator plate according to claim 1, wherein a mesa
structure is formed at a position of the vibrating part, the
position on which the first excitation electrode and the second
excitation electrode are formed, so that a central region of the
vibrating part is thicker than a region surrounding the central
region.
7. The crystal resonator plate according to claim 1, wherein at
least one groove is disposed in at least one of the vibrating part
and the holding part, and wherein the at least one groove is
inclined toward a central part of the vibrating part relative to an
X axis direction of the AT-cut crystal.
8. The crystal resonator plate according to claim 7, wherein the at
least one groove is constituted by: one or more first grooves
formed in the first main surface of the vibrating part; and one or
more second grooves formed in the second main surface of the
vibrating part, and wherein the one or more first grooves and the
one or more second grooves are alternately arranged in the
vibrating part, from a side of the vibrating part to a side of the
external frame part.
9. The crystal resonator plate according to claim 1, wherein the
external frame part includes a recessed part that is disposed at a
position to be connected to the holding part in at least one of the
first main surface and the second main surface, and wherein
respective thicknesses of the external frame part, the recessed
part and the holding part have a relation represented by the
following expression: (thickness of the external frame
part)>(thickness of the recessed part).gtoreq.(thickness of the
holding part).
10. The crystal resonator plate according to claim 9, wherein the
recessed part is formed in each of the first main surface and the
second main surface.
11. The crystal resonator plate according to claim 9, wherein a
bottom surface of the recessed part is formed so as to be a same
surface as a surface of the holding part.
12. The crystal resonator plate according to claim 9, wherein a
bottom surface of the recessed part is formed so that there is a
step between the bottom surface of the recessed part and a surface
of the holding part.
13. The crystal resonator plate according to claim 9, wherein, when
a width direction is set to a direction orthogonal to the
protruding direction of the holding part from the external frame
part, viewing from a direction perpendicular to the main surface of
the external frame part, a width of the recessed part is larger
than a width of the holding part.
14. The crystal resonator plate according to claim 9, wherein an
interior wall surface of the recessed part has a curvature when
viewed from a direction perpendicular to a main surface of the
external frame part.
15. A crystal resonator device comprising: the crystal resonator
plate according to claim 1, a first sealing member covering the
first main surface of the crystal resonator plate; and a second
sealing member covering the second main surface of the crystal
resonator plate.
Description
TECHNICAL FIELD
[0001] The present invention relates to an AT-cut crystal resonator
plate having a first main surface on which a first excitation
electrode is formed and a second main surface on which a second
excitation electrode is formed, and to a crystal resonator device
in which the crystal resonator plate is mounted.
BACKGROUND ART
[0002] Patent Document 1 discloses a piezoelectric resonator
including: a piezoelectric resonator plate provided with excitation
electrodes; a support frame disposed so as to surround the
piezoelectric resonator plate; and coupling parts that couple the
piezoelectric resonator plate to the support frame. In this
piezoelectric resonator, the coupling parts are constituted by a
first coupling part and a second coupling part each connecting a
corresponding corner of the vibrating part respectively to
different corners of the support frame in the -X direction. An end
of the piezoelectric resonator plate in the -X direction is
supported by the support frame in a cantilevered manner.
[0003] Patent Documents 2 and 3 are known as inventions related to
an AT-cut crystal resonator whose main vibration mode is a
thickness shear vibration. The At-cut crystal resonator is suitable
for downsizing and increasing the frequency and has excellent
frequency temperature characteristics.
[0004] When the crystal axes of a synthetic crystal are
respectively referred to as an X axis, a Y axis and a Z axis, an
AT-cut crystal resonator is obtained by rotating the synthetic
crystal about the X axis by 35.degree. 15'. Note that, in the
present description, the Y axis after rotated by 35.degree. 15' is
referred to as a Y' axis, and the Z axis after rotated by
35.degree. 15' is referred to as a Z' axis.
[0005] Patent Document 2 discloses a crystal resonator 100
including: a vibrating part 300 that is provided with excitation
electrodes 200; a frame part 500 surrounding the vibrating part
300; and connecting parts 400 that connect the frame part 500 to
the vibrating part 300. In this crystal resonator 100, the
connecting parts 400 are connected to the frame part 500 at three
positions (each corner parts and a central part) on one end side
(i.e. at six positions on both end sides) of the vibrating part 300
in the X axis direction of the crystal axes (see FIG. 15).
[0006] Also, Patent Document 3 discloses a piezoelectric resonator
plate including: a vibrating part having main surfaces on which
excitation electrodes are respectively formed; a frame part
arranged on an outer circumferential side of the vibrating part via
a through groove; and support parts connecting the vibrating part
to the frame part. Sawtooth notches are formed on a front side and
a rear side of each respective support part along its width
direction.
PRIOR ART DOCUMENTS
Patent Documents
[0007] [Patent Document 1] JP 2011-091173 A
[0008] [Patent Document 2] JP 1106-083011 B
[0009] [Patent Document 3] JP 2007-214942 A
SUMMARY OF THE INVENTION
Problem to be Solved by the Invention
[0010] Problems related to the inventions according to Patent
Documents 1 to 3 will be described with reference to FIGS. 15 and
16. FIG. 15 is a plan view of a conventional crystal resonator
plate. FIG. 16(a) is an explanatory diagram explaining a vibration
deflection of the crystal resonator plate. FIG. 16(b) is a graph
indicating a charge distribution of the crystal resonator plate in
the X axis direction. FIG. 16(c) is a graph indicating a charge
distribution of the crystal resonator plate in the Z' axis
direction. In the graphs shown in FIGS. 16(b) and 16(c), the
horizontal axis represents the position in the crystal resonator
plate, and the vertical axis represents a charge quantity at each
position.
[0011] As it can be seen from FIG. 16(a), which explains the
vibration deflection of the crystal resonator plate, it is
generally known that the thickness shear vibration occurs when a
voltage is applied to the crystal resonator plate, and that the X
axis direction is dominant as the vibration direction of the
crystal resonator plate, which results in the displacement of the
piezoelectric vibration in the X axis direction larger than that in
the Z' axis direction.
[0012] For this reason, if the piezoelectric resonator plate is
held in the X axis direction in which the piezoelectric vibration
is large as described in Patent document 1 (i.e. an end of the
piezoelectric resonator plate in the -X direction is supported in a
cantilevered manner), a vibration leakage of the piezoelectric
resonator plate is likely to occur via the first coupling part and
the second coupling part, which may reduce the piezoelectric
vibration efficiency. That is, in order to hold the piezoelectric
resonator plate by the coupling part, it is not preferable to
dispose the coupling part along the X axis direction in which the
piezoelectric vibration is dominant.
[0013] According to the graph of FIG. 16(b) that indicates the
charge distribution of the crystal resonator plate in the X axis
direction, it can be seen that the charge distribution is large at
the central position of the crystal resonator plate. In contrast,
according to FIG. 16(c) that indicates the charge distribution of
the crystal resonator plate in the Z' direction, the charge
distribution is substantially uniform, although it has a tendency
to slightly decrease toward both ends of the crystal resonator
plate. From this, when the voltage is applied to the crystal
resonator plate in order to cause the piezoelectric vibration, it
can be seen that, in the X axis direction, the displacement of the
piezoelectric vibration is large at the central part where the
charge distribution is large. On the other hand, the charge
distribution is substantially uniform in the Z' direction, thus it
can be seen that the displacement of the piezoelectric vibration is
uniform.
[0014] In brief, it can be seen, from the graphs of FIGS. 16(b) and
16(c), that if the crystal resonator plate that is being
piezoelectrically vibrated is held at the central part thereof in
the X axis direction in which the displacement of the piezoelectric
vibration is large, the piezoelectric vibration is prevented, thus
the piezoelectric vibration efficiency degrades.
[0015] In view of the above, when the vibrating part 300 is
connected at the central position thereof in the X axis direction
to the frame part 500, for example in the AT-cut crystal resonator
as shown in Patent Document 2, the vibration leakage is likely to
occur compared to the corner part because the displacement of the
piezoelectric vibration at the central position is large. Thus, the
piezoelectric vibration of the vibrating part 300 is prevented,
which degrades the piezoelectric vibration efficiency.
[0016] The present invention was made in consideration of the above
circumstances, an object of which is to provide an AT-cut crystal
resonator plate having a high piezoelectric vibration efficiency to
cause the piezoelectric vibration efficiently, and to provide a
crystal resonator device including the crystal resonator plate.
Means for Solving the Problem
[0017] In order to achieve the above object, the present invention
includes a configuration described below.
[0018] A crystal resonator plate according to the present invention
is an AT-cut crystal resonator plate including a first main surface
on which a first excitation electrode is formed and a second main
surface on which a second excitation electrode formed. The AT-cut
crystal resonator plate further includes: a substantially
rectangular-shaped vibrating part having the first excitation
electrode and the second excitation electrode; a holding part
protruding from a corner part of the vibrating part in a Z' axis
direction of the AT-cut crystal; and an external frame part
configured to surround an external circumference of the vibrating
part and to hold the holding part.
[0019] In the crystal resonator plate having the above-described
configuration of the present invention, the holding part is
protruded from the corner part of the vibrating part in the Z' axis
direction of the AT-cut crystal so as to be held by the external
frame part. Thus, unlike the conventional crystal resonator plate,
the vibrating part is not held at the central position on the side
along the X axis direction. Therefore, when the crystal resonator
plate is piezoelectrically vibrated, it is possible to cause an
efficient piezoelectric vibration.
[0020] The crystal resonator plate as described above may have a
configuration in which the first excitation electrode and the
second excitation electrode are each formed at a position spaced
apart from a region on an extended line of the holding part in the
Z' axis direction toward a central direction of the vibrating
part.
[0021] With the above-described configuration, the first excitation
electrode and the second excitation electrode are not formed on the
extended line of the holding part in the Z' axis direction. As a
result, the piezoelectric vibration of the crystal resonator plate
can be prevented from leaking along the holding part to the
external frame part, thus, it is possible to confine the
piezoelectric vibration of the crystal resonator plate in the
vibrating part.
[0022] In the crystal resonator plate as described above, the
holding parts may be respectively protruded toward the external
frame part from two corner parts disposed in the vibrating part in
the Z' axis direction.
[0023] In this case, the vibrating part of the crystal resonator
plate is held by the external frame part via the holding parts
respectively extended from the two corner parts of the vibrating
part in the Z' axis direction. Thus, the vibrating part can be
reliably held. Furthermore, the respective wiring patterns of the
first excitation electrode and the second excitation electrode that
are formed respectively on both main surfaces of the crystal
resonator plate can be independently disposed via the respective
holding parts protruded from the two corner parts. Thus, it is
possible to suppress the parasitic capacitance between the wiring
patterns, which prevents reduction in the frequency variation
amount.
[0024] In the above-described crystal resonator plate, the holding
part may be protruded toward the external frame part from one
corner part disposed in the vibrating part.
[0025] In this case, the vibrating part of the crystal resonator
plate is held by the external frame part via the holding part that
is protruded from one corner part toward the external frame part.
Since the number of the holding parts is reduced, it is possible to
further suppress the vibration leakage to the external frame part.
Also, compared to the configuration having two holding parts, it is
possible to reduce the stress application rate, which results in
reduction in the frequency shift due to the stress. Thus, the
piezoelectric vibration of the crystal resonator plate can be
stably caused.
[0026] The above-described crystal resonator plate may have a
configuration in which the external frame part has a thickness
larger than a thickness of the holding part.
[0027] With the above-described configuration, because of the
difference in the thickness between the external frame part and the
holding part, the natural frequency of the piezoelectric vibration
is also different between the external frame part and the holding
part. Thus, when the vibrating part is piezoelectrically vibrated,
the external frame part hardly resonates with the piezoelectric
vibration of the holding part.
[0028] The above-described crystal resonator plate may have a
configuration in which a mesa structure is formed at a position of
the vibrating part, the position on which the first excitation
electrode and the second excitation electrode are formed, so that a
central region of the vibrating part is thicker than a region
surrounding the central region.
[0029] In this case, the mesa structure is formed at the position
of the vibrating part, on which the first excitation electrode and
the second excitation electrode are formed. Thus, the parts to be
piezoelectrically vibrated have different thicknesses, which
results in difference in the frequency of the piezoelectric
vibration. Since a boundary between different frequencies can be
formed, it is possible to improve an effect of confining the
piezoelectric vibration. By confining thus the piezoelectric
vibration, the piezoelectric vibration can be prevented from
leaking.
[0030] The above-described crystal resonator plate may have a
configuration in which a groove is disposed in at least one of the
vibrating part and the holding part, and the groove is inclined
toward a central part of the vibrating part relative to an X axis
direction of the AT-cut crystal.
[0031] In this case, when the crystal resonator plate is
piezoelectrically vibrated, the groove formed in the vibrating part
prevents the piezoelectric vibration from leaking outside the
vibrating part. Thus, it is possible to confine the piezoelectric
vibration in the vibrating part.
[0032] The above-described crystal resonator plate may have a
configuration in which the groove is constituted by: one or more
first grooves formed in the first main surface of the vibrating
part; and one or more second grooves formed in the second main
surface of the vibrating part, and also may have a configuration in
which the one or more first grooves and the one or more second
grooves are alternately arranged in the vibrating part, from a side
of the vibrating part to a side of the external frame part.
[0033] In this case, since the first groove(s) and the second
groove(s) are alternately arranged in the holding part, from the
side of the vibrating part to the side of the external frame part.
Thus, it is possible to improve an effect of confining the
piezoelectric vibration.
[0034] A crystal resonator device according to the present
invention includes: the above-described crystal resonator plate; a
first sealing member covering the first main surface of the crystal
resonator plate; and a second sealing member covering the second
main surface of the crystal resonator plate.
[0035] With the above-described configuration in which the crystal
resonator plate is interposed between the first sealing member and
the second sealing member, it is possible to manufacture a
relatively downsized crystal resonator device. Also, since the
crystal resonator plate has the features as described above, it is
possible to prevent the vibration leakage and to obtain,
accordingly, a crystal resonator device having a high piezoelectric
vibration efficiency to cause efficiently the piezoelectric
vibration.
[0036] In the above-described crystal resonator plate, the external
frame part may include a recessed part that is disposed at a
position to be connected to the holding part in at least one of the
first main surface and the second main surface. The respective
thicknesses of the external frame part, the recessed part and the
holding part may have a relation represented by the following
expression: (thickness of the external frame part)>(thickness of
the recessed part).gtoreq.(thickness of the holding part).
[0037] In this case, when an impact or the like acts on the crystal
resonator device, the recessed part serves to avoid or relax the
stress concentration at the connecting part of the external frame
part and the holding part, which leads to improvement in shock
resistance of the crystal resonator device. Furthermore, the
recessed part serves to suppress the vibration leakage from the
vibrating part to the external frame part. That is, when the
vibration leaks from the vibrating part, it may pass through the
holding part to reach the external frame part. However, because the
recessed part is disposed in the position where the vibration leaks
from the holding part to the external frame part, it is possible to
adjust the vibration leakage to prevent resonance with the external
frame part, thus the vibration is not likely to be transmitted to
the external frame part.
[0038] In the above-described crystal resonator plate, the recessed
part may be formed in each of the first main surface and the second
main surface.
[0039] In this case, it is possible to further improve the shock
resistance of the crystal resonator device due to the recessed
parts that are formed in both main surfaces.
[0040] In the above-described crystal resonator plate, the bottom
surface of the recessed part may be formed so as to be the same
surface as the surface of the holding part.
[0041] In this case, since there is no step between the bottom
surface of the recessed part and the surface of the holding part,
it is possible to avoid the stress concentration at the connecting
part between the external frame part and the holding part, which
leads to improvement in shock resistance of the crystal resonator
device.
[0042] In the above-described crystal resonator plate, a bottom
surface of the recessed part may be formed so that there is a step
between the bottom surface of the recessed part and the surface of
the holding part.
[0043] In this case, the step remains at the connecting part of the
external frame part and the holding part. However, the external
frame part itself also has a step at the boundary between the
region where the recessed part is formed and the other region. In
this way, when an impact or the like acts on the crystal resonator
device, the stress is distributed to the above two step parts. As a
result, it is possible to relax the stress concentration at the
connecting part of the external frame part and the holding part,
which leads to improvement in shock resistance of the crystal
resonator device.
[0044] In the above-described crystal resonator plate, when a width
direction is set to a direction orthogonal to the protruding
direction of the holding part from the external frame part, viewing
from a direction perpendicular to the main surface of the external
frame part, a width of the recessed part may be larger than a width
of the holding part.
[0045] In this case, since the width of the recessed part is larger
than the width of the holding part, it is possible to improve an
effect of the stress distribution by the recessed part or to
improve an effect of vibration damping.
[0046] In the above-described crystal resonator plate, an interior
wall surface of the recessed part may have a curvature when viewed
from a direction perpendicular to the main surface of the external
frame part.
[0047] In this case, the interior wall surface of the recessed part
can have a shape with no vertex. Thus, it is possible to avoid the
stress concentration on the vertex.
Effect of the Invention
[0048] The present invention can provide an AT-cut crystal
resonator plate having a high piezoelectric vibration efficiency to
cause efficiently the piezoelectric vibration, and a crystal
resonator device including the above AT-cut crystal resonator
plate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0049] FIG. 1 is a schematic configuration diagram showing
respective components of an embodiment of a crystal resonator
according to the present invention.
[0050] FIG. 2 is a schematic plan view of a first sealing member of
the crystal resonator according to the embodiment of the present
invention.
[0051] FIG. 3 is a schematic bottom view the first sealing member
of the crystal resonator according to the embodiment of the present
invention.
[0052] FIG. 4A is a schematic plan view of the crystal resonator
plate of a first embodiment according to the present invention.
[0053] FIG. 4B is a schematic plan view of another example of the
crystal resonator plate in the first embodiment according to the
present invention.
[0054] FIG. 5 is a schematic bottom view of the crystal resonator
plate of the first embodiment according to the present
invention.
[0055] FIG. 6A is a cross-sectional view taken from line A-A of
FIG. 4A.
[0056] FIG. 6B is a cross-sectional view taken from line B-B of
FIG. 4B.
[0057] FIG. 6C is a cross-sectional view of another example of the
crystal resonator plate according to the present invention.
[0058] FIG. 7 is a schematic plan view of a second sealing member
of the crystal resonator according to the embodiment of the present
invention.
[0059] FIG. 8 is a schematic bottom view of the second sealing
member of the crystal resonator according to the embodiment of the
present invention.
[0060] FIG. 9 is a schematic plan view of a first variation of the
crystal resonator plate in the first embodiment according to the
present invention.
[0061] FIG. 10 is a schematic plan view of a second variation of
the crystal resonator plate in the first embodiment according to
the present invention.
[0062] FIG. 11 is a schematic plan view of a third variation of the
crystal resonator plate in the first embodiment according to the
present invention.
[0063] FIG. 12 is a schematic plan view of a fourth variation of
the crystal resonator plate in the first embodiment according to
the present invention.
[0064] FIG. 13 is a cross-sectional view taken from line c-c of
FIG. 12.
[0065] FIG. 14 is a schematic plan view of the crystal resonator
plate of a second embodiment according to the present
invention.
[0066] FIG. 15 is a plan view of a conventional crystal resonator
plate.
[0067] FIG. 16(a) is an explanatory diagram explaining a vibration
deflection of the crystal resonator plate. FIG. 16(b) is a graph
indicating a charge distribution of the crystal resonator plate in
an X axis direction among the crystal axes. FIG. 16(c) is a graph
indicating a charge distribution of the crystal resonator plate in
a Z axis direction among the crystal axes.
[0068] FIG. 17 is a schematic plan view of the crystal resonator
plate of a third embodiment according to the present invention.
[0069] FIG. 18(a) is a perspective view showing a connecting
structure of a holding part and an external frame part when the
external frame part is provided with no recessed part. FIG. 18(b)
is a perspective view showing a connecting structure of the holding
part and the external frame part when the connecting structure is
formed so that a bottom surface of a recessed part is the same
surface as a surface of the holding part. FIG. 18(c) is a
perspective view showing a connecting structure of the holding part
and the external frame part when the connecting structure is formed
so as to have a step between the bottom surface of the recessed
part and the surface of the holding part.
[0070] FIG. 19(a) is a plan view showing a variation of the shape
of the recessed part. FIG. 19(b) is a plan view showing another
variation of the shape of the recessed part.
[0071] FIG. 20 is a diagram showing the crystal plate. The upper
portion is a plan view showing the crystal plate after it is
subjected to an etching for forming an external form. The lower
portion is a cross-sectional view taken from line A-A of the upper
portion.
[0072] FIG. 21A is a diagram showing the crystal plate. The upper
portion is a plan view showing the crystal plate after it is
subjected to an etching for forming a mesa. The lower portion is a
cross-sectional view taken from line A-A of the upper portion.
[0073] FIG. 21B is a diagram showing the crystal plate. The upper
portion is a plan view showing the crystal plate after it is
subjected to an etching for forming a mesa. The lower portion is a
cross-sectional view taken from line A-A of the upper portion.
[0074] FIG. 22A is a diagram showing the crystal plate. The upper
portion is a plan view showing the crystal plate after it is
subjected to an etching for frequency adjustment. The lower portion
is a cross-sectional view taken from line A-A of the upper
portion.
[0075] FIG. 22B is a diagram showing the crystal plate. The upper
portion is a plan view showing the crystal plate after it is
subjected to an etching for frequency adjustment. The lower portion
is a cross-sectional view taken from line A-A of the upper
portion.
[0076] FIG. 23 is a diagram showing the crystal plate. The upper
portion is a plan view showing the crystal plate after it is
subjected to an etching for frequency adjustment. The lower portion
is a cross-sectional view taken from line A-A of the upper
portion.
MODES FOR CARRYING OUT THE INVENTION
[0077] Hereinafter, three embodiments of the crystal resonator
device according to the present invention will be described. The
description of the embodiments will be given on the subject matters
in the order of: the configuration of the crystal resonator device;
the method for manufacturing the crystal resonator device; and
functions and effects of the crystal resonator device.
Configuration of Crystal Resonator Device according to First
Embodiment
[0078] The configuration of a crystal resonator device 1 according
to the present invention is described with reference to FIG. 1.
FIG. 1 is a schematic configuration diagram showing respective
components of an embodiment of the crystal resonator.
[0079] In the drawings, parts corresponding to electrodes are shown
by hatching. Also, in cross-sectional views described later, only
the parts corresponding to the electrodes are shown by hatching,
and the other parts are not hatched to enhance the visibility of
the drawings.
[0080] The crystal resonator device 1 according to the present
invention is, for example, a crystal resonator including: a crystal
resonator plate 2; a first sealing member 3 that covers and
hermetically seals a first main surface 2a of the crystal resonator
plate 2; and a second sealing member 4 that covers and hermetically
seals a second main surface 2b of the crystal resonator plate 2. In
the crystal resonator device 1, the crystal resonator plate 2 is
bonded to the first sealing member 3, and also is bonded to the
second sealing member 4.
[0081] That is, the crystal resonator device 1 is made as a package
12 having a sandwich structure in which an internal space 13 is
hermetically sealed, more specifically, the internal space 13
between the first sealing member 3 and the crystal resonator plate
2, and the internal space 13 between the crystal resonator plate 2
and the second sealing member 4 (see FIG. 1).
[0082] The crystal resonator device 1 has a package size of
1.0.times.0.8 mm, which is reduced in size and height. According to
the size reduction, no castellation is formed in the package 12. As
described later, through holes (a first through hole h1, a second
through hole h2, and a third through hole h3) are used for
conduction between electrodes.
[0083] As shown in FIG. 1, the internal space 13 is located so as
to be deflected to one end side (left side) of the package 12 in
plan view.
[0084] Hereinafter, each components will be described.
First Sealing Member
[0085] The first sealing member 3 of the crystal resonator device 1
according to the present invention is described with reference to
FIGS. 2 and 3. FIG. 2 is a schematic plan view of the first sealing
member. FIG. 3 is a schematic bottom view of the first sealing
member.
[0086] The first sealing member 3 is made of a material having the
flexural rigidity (moment of inertia of area.times.Young's modulus)
of not more than 1000 [Nmm.sup.2]. Specifically, as shown in FIGS.
2 and 3, the first sealing member 3 is a substrate having a
rectangular parallelepiped shape that is made of a single glass
wafer or a single crystal wafer. The first main surface 3a is an
upper surface. The second main surface 3b (the surface to be bonded
to the crystal resonator plate 2) is formed as a smooth flat
surface (mirror finished).
[0087] On the second main surface 3b of the first sealing member 3,
a sealing-member-side first bonding pattern 31 to be bonded to the
crystal resonator plate 2 is disposed so as to enclose the internal
space 13. As shown in FIG. 3, the sealing-member-side first bonding
pattern 31 is located so as to be deflected to the left side in
plan view of the second main surface 3b of the first sealing member
3. The sealing-member-side first bonding pattern 31 has a constant
line width at all positions.
[0088] The sealing-member-side first bonding pattern 31 is
constituted by a base PVD film deposited on the first sealing
member 3 by the physical vapor deposition, and an electrode PVD
film deposited on the base PVD film by the physical vapor
deposition. In this embodiment, the base PVD film is made of Ti (or
Cr), and the electrode PVD film is made of Au. Also, the
sealing-member-side first bonding pattern 31 does not contain
Sn.
Crystal Resonator Plate
[0089] An embodiment of the crystal resonator plate 2 according to
the present invention is described with reference to FIGS. 4 to 6.
FIG. 4A is a schematic plan view of the crystal resonator plate of
the first embodiment. FIG. 4B is a schematic plan view of another
example of the crystal resonator plate in the first embodiment.
FIG. 5 is a schematic bottom view of the crystal resonator plate of
the first embodiment. FIG. 6A is a cross-sectional view taken from
line A-A of FIG. 4A. FIG. 6B is a cross-sectional view taken from
line B-B of FIG. 4B. FIG. 6C is a cross-sectional view of another
example of the crystal resonator plate.
[0090] The crystal resonator plate 2 according to this embodiment
is an AT-cut crystal processed by rotating a rectangular-shaped
crystal plate about the X axis among the crystal axes by 35.degree.
15'. The crystal resonator plate 2 includes: a vibrating part 21;
holding parts 22; and an external frame part 23 (see FIGS. 4A and
5). In the present description, the crystal axes of a synthetic
crystal are referred to as the X axis, the Y axis and the Z axis,
and the Y axis and the Z axis when rotating the AT-cut crystal
about the X axis by 35.degree. 15' are respectively referred to as
a Y' axis and a Z' axis.
[0091] The crystal resonator plate 2 in the examples shown in the
drawings has cut-out parts formed by cutting out the
rectangular-shaped crystal plate. The cut-out parts are constituted
by an inversed U-shaped part k1 in plan view and an oblong
rectangular part k2 in plan view. The crystal resonator plate 2 is
made of a crystal that is a piezoelectric material, and both main
surfaces thereof (i.e., the first main surface 2a and the second
main surface 2b) are each formed as a smooth flat surface (mirror
finished).
[0092] The vibrating part 21 has a substantially rectangular shape
and is piezoelectrically vibrated upon voltage application. The
vibrating part 21 is not required to have square corner parts. The
corner parts may be chamfered when the vibrating part 21 is formed
by wet etching. A first excitation electrode 211 and a second
excitation electrode 212 are respectively formed on the first main
surface 2a and the second main surface 2b of the vibrating part 21
so as to apply a voltage to the vibrating part 21. At the position
of the vibrating part 21 on which the first excitation electrode
211 and the second excitation electrode 212 are formed, a mesa
structure 213 may be formed so that the central region of the
vibrating part 21 is thicker than the region surrounding the
central region (see FIG. 6A). In this case, since the central part
of the crystal resonator plate 2 has a larger thickness as the mesa
structure 213, it is possible to improve an effect of confining the
piezoelectric vibration.
[0093] The first excitation electrode 211 and the second excitation
electrode 212 are formed at a position spaced apart from the region
on the extended line of the holding parts 22 (described later) in
the Z' axis direction toward the central direction of the vibrating
part 21. Thus, the first excitation electrode 211 and the second
excitation electrode 212 are not formed on the extended line of the
holding parts 22 in the Z' axis direction. Accordingly, it is
possible to keep a relatively long distance between the region
where the crystal resonator plate 2 is piezoelectrically vibrated
and the holding parts 22. As a result, the piezoelectric vibration
of the crystal resonator plate 2 can be prevented from leaking
along the holding parts 22 to the external frame part 23, thus, it
is possible to confine the piezoelectric vibration of the crystal
resonator plate 2 in the vibrating part 21.
[0094] The first excitation electrode 211 and the second excitation
electrode 212 are each constituted by a base PVD film (Ti or Cr)
deposited on the vibrating part 21 by the physical vapor
deposition, and an electrode PVD film (Au) deposited on the base
PVD film by the physical vapor deposition.
[0095] The first excitation electrode 211 and the second excitation
electrode 212 are extracted outside the vibrating part 21 via the
holding parts 22 and 22 on which are respectively formed a first
extraction electrode 214 and a second extraction electrode 215 that
extract the respective excitation electrodes. In the examples shown
in the drawings, on the first main surface 2a, the first extraction
electrode 214 is extracted from the corner part of the first
excitation electrode 211. On the second main surface 2b, the second
extraction electrode 215 is extracted from the corner part of the
second excitation electrode 212 so that its extracted direction is
opposite to the direction in which the first extraction electrode
214 is extracted on the first main surface 2a (see FIG. 6A).
[0096] The holding parts 22 and 22 are protruded from the
respective corner parts of the rectangular shaped vibrating part 21
in the Z' direction of the AT-cut crystal. In this embodiment, the
holding parts 22 and 22 are protruded respectively from the two
corner parts 21a disposed in the vibrating part 21 in the Z'
direction toward the external frame part 23 (see FIGS. 4A and 5).
In the examples shown in the drawings, the first excitation
electrode 211 is extracted via the holding part 22 on the left side
in plan view (in the -Z' axis direction), and the second excitation
electrode 212 is extracted via the holding part 22 on the right
side in bottom view (in the +Z' axis direction).
[0097] The external frame part 23 surrounds the external
circumference of the vibrating part 21 and holds the holding parts
22. On the first main surface 2a, a resonator-plate-side first
bonding pattern 216 is formed so as to be bonded to the first
sealing member 3. On the second main surface 2b, a
resonator-plate-side second bonding pattern 217 is formed so as to
be bonded to the second sealing member 4. As shown in FIG. 1, the
resonator-plate-side first bonding pattern 216 and the
resonator-plate-side second bonding pattern 217 are located so as
to be deflected to the left side in plan view of both main surfaces
2a and 2b.
[0098] The resonator-plate-side first bonding pattern 216 and the
resonator-plate-side second bonding pattern 217 are each
constituted by a base PVD film (Ti or Cr) deposited on the external
frame part 23 by the physical vapor deposition, and an electrode
PVD film (Au) deposited on the base PVD film by the physical vapor
deposition. The resonator-plate-side first bonding pattern 216 and
the resonator-plate-side second bonding pattern 217 do not contain
Sn. That is, the same materials as the materials for the first
excitation electrode 211 and the second excitation electrode 212
are used. Also, the resonator-plate-side first bonding pattern 216
and the resonator-plate-side second bonding pattern 217 may be made
of electrode materials different from those for the first
excitation electrode 211 and the second excitation electrode
212.
[0099] The first through hole h1 is formed in the external frame
part 23. The first through hole h1 is to extract, to the side of
the second main surface 2b, the resonator-plate-side first bonding
pattern 216 that is connected to the first excitation electrode
211. The first through hole h1 is disposed in the outward position
of the internal space 13, and located so as to be deflected to the
other end side (right side) in plan view of both main surfaces 2a
and 2b, as shown in FIG. 1. Thus, the first through hole h1 is not
formed in the inward position of the internal space 13. Here, the
inward position of the internal space 13 means strictly the inner
side of the inner peripheral surface of the bonding material 11,
not including the position on the bonding material 11
(resonator-plate-side first bonding pattern 216).
[0100] It is preferable that the thickness of the external frame
part 23 is larger than the thickness of the holding parts 22 (see
FIG. 6A). In this case, because of the difference in the thickness
between the external frame part 23 and the holding parts 22, the
natural frequency of the piezoelectric vibration is also different
between the external frame part 23 and the holding parts 22. Thus,
the external frame part 23 hardly resonates with the piezoelectric
vibration of the holding parts 22. Also, it is possible to enlarge
each space between the piezoelectric resonator plate 2 and the
first sealing member 3, and between the piezoelectric resonator
plate 2 and the second sealing member 4. Thus, the vibrating part
21 of the piezoelectric resonator plate 2 can be prevented from
making contact with the first sealing member 3 or the second
sealing member 4.
[0101] Generally, the piezoelectric vibration is not likely to
transmit from the thick part to the thin part, accordingly, an
effect of blocking the piezoelectric vibration is provided.
[0102] In view of the above, as another example of the crystal
resonator plate 2 of this embodiment, the thickness of the holding
part 22 may be larger than the thickness of the vibrating part 21,
as shown in FIGS. 4B and 6B. In this case, each boundary between
the holding parts 22 and the vibrating part 21 is formed at a
position where the thickness of the holding part 22 differs from
the thickness of the vibrating part 21. Thus, it is possible to not
consider the unnecessary vibration including the vibration of the
holding parts 22 when considering the piezoelectric vibration of
the vibrating part 21.
[0103] Also, as another example of the crystal resonator plate 2 of
this embodiment, the thickness of the holding part 22 may be
smaller than the thickness of the mesa structure 213 of the
vibrating part 21, as shown in FIG. 6C. In this case, since the
thickness of the holding part 22 is smaller than the thickness of
the mesa structure 213, the holding part 22 is not likely to
resonate with the vibrating part 21. Thus, it is possible to
efficiently prevent the vibration energy of the vibrating part 21
from transmitting to the holding part and being lost.
Second Sealing Member
[0104] The second sealing member of the crystal resonator device
according to the present invention is described with reference to
FIGS. 7 and 8. FIG. 7 is a schematic plan view of the second
sealing member of the crystal resonator. FIG. 8 is a schematic
bottom view of the second sealing member of the crystal
resonator.
[0105] The second sealing member 4 is made of a material having the
flexural rigidity (moment of inertia of area.times.Young's modulus)
of not more than 1000 [Nmm.sup.2]. Specifically, as shown in FIG.
7, the second sealing member 4 is a substrate having a rectangular
parallelepiped shape that is made of a single glass wafer or a
single crystal wafer. A first main surface 4a (the surface to be
bonded to the crystal resonator plate 2) of the second sealing
member 4 is formed as a smooth flat surface (mirror finished).
[0106] On the first main surface 4a of the second sealing member 4,
a sealing-member-side second bonding pattern 41 to be bonded to the
crystal resonator plate 2 is disposed so as to enclose the internal
space 13. As shown in FIGS. 1 and 7, the sealing-member-side second
bonding pattern 41 is located so as to be deflected to the left
side in plan view of the first main surface 4a of the second
sealing member 4. The sealing-member-side second bonding pattern 41
has a constant line width at all positions.
[0107] The sealing-member-side second bonding pattern 41 is
constituted by a base PVD film deposited on the second sealing
member 4 by the physical vapor deposition, and an electrode PVD
film deposited on the base PVD film by the physical vapor
deposition.
[0108] In this embodiment, the base PVD film is made of Ti (or Cr),
and the electrode PVD film is made of Au. Also, the
sealing-member-side second bonding pattern 41 does not contain
Sn.
[0109] On the second main surface 4b of the second sealing member
4, a pair of external electrode terminals (a first external
electrode terminal 42a and a second external electrode terminal
42b) to be electrically connected to the outside is disposed (see
FIG. 8). Note that the number of the external electrode terminals
is not limited to two. Three or more external electrode terminals
may be disposed.
[0110] The first external electrode terminal 42a is electrically
connected, directly, to the first excitation electrode 211 via the
resonator-plate-side first bonding pattern 216. The second external
electrode terminal 42b is electrically connected, directly, to the
second excitation electrode 222 via the resonator-plate-side second
bonding pattern 217.
[0111] As shown in FIG. 8, the first external electrode terminal
42a and the second external electrode terminal 42b are respectively
located on both ends in the longitudinal direction in plan view of
the second main surface 4b of the second sealing member 4. The pair
of external electrode terminals (the first external electrode
terminal 42a and the second external electrode terminal 42b) is
each constituted by a base PVD film deposited on the second main
surface 4b by the physical vapor deposition, and an electrode PVD
film deposited on the base PVD film by the physical vapor
deposition.
[0112] Compared to each base PVD film of the above-described
resonator-plate-side first bonding pattern 216, the
resonator-plate-side second bonding pattern 217, the
sealing-member-side first bonding pattern 31 and the
sealing-member-side second bonding pattern 41, each base PVD film
of the external electrode terminals (the first external electrode
terminal 42a and the second external electrode terminal 42b) has a
large thickness. Also, the first external electrode terminal 42a
and the second external electrode terminal 42b each cover a region
of not less than 1/3 of the area of the second main surface 4b of
the second sealing member 4.
[0113] In the second sealing member 4, as shown in FIGS. 1, 7 and
8, two through holes (the second through hole h2 and the third
through hole h3) are formed. The second through hole h2 and the
third through hole h3 are disposed in the outward position of the
internal space 13. As shown in FIG. 7, the second through hole h2
is located on the right side in plan view of both main surfaces
(the first main surface 4a and the second main surface 4b) and the
third through hole h3 is located on the upper left side in plan
view. That is, the second through hole h2 and the third through
hole h3 are not formed in the inward position of the internal space
13.
[0114] Here, the inward position of the internal space 13 means
strictly the inner side of the inner peripheral surface of the
bonding material 11, not including the position on the bonding
material 11 (the sealing-member-side second bonding pattern
41).
Method for Manufacturing Crystal Resonator Device of First
Embodiment
[0115] Here, description is given on a method for manufacturing the
crystal resonator device 1 using the above-described components,
i.e. the crystal resonator plate 2, the first sealing member 3 and
the second sealing member 4.
[0116] The first sealing member 3 is bonded to the crystal
resonator plate 2 in a state in which the resonator-plate-side
first bonding pattern 216 of the crystal resonator plate 2 and the
sealing-member-side first bonding pattern 31 of the first sealing
member 3 are overlapped with each other.
[0117] Similarly to the above, the second sealing member 4 is
bonded to the crystal resonator plate 2 in a state in which the
resonator-plate-side second bonding pattern 217 of the crystal
resonator plate 2 and the sealing-member-side second bonding
pattern 41 of the second sealing member 4 are overlapped with each
other.
[0118] Thus, the first sealing member 3 is bonded to the crystal
resonator plate 2, and the first sealing member 3 is bonded to the
crystal resonator plate 2, by being subjected to diffusion bonding
in a state in which each bonding pattern is overlapped with the
corresponding bonding pattern. Using the diffusion bonding as the
bonding method can prevent generation of gas that occurs in case of
bonding using an adhesive and the like, however, it is possible to
use a publicly known special bonding material such as an
adhesive.
[0119] In the package 12 manufactured as described above, the first
sealing member 3 and the crystal resonator plate 2 have a gap of
not more than 1.00 .mu.m. The second sealing member 4 and the
crystal resonator plate 2 have a gap of not more than 1.00 .mu.m.
That is, the thickness of the bonding material 11 between the first
sealing member 3 and the crystal resonator plate 2 is not more than
1.00 .mu.m, and the thickness of the bonding material 11 between
the second sealing member 4 and the crystal resonator plate 2 is
not more than 1.00 .mu.m (specifically, the thickness in the Au-Au
bonding of this embodiment is 0.15 to 1.00 .mu.m). As a comparative
example, the conventional metal paste sealing material containing
Sn has a thickness of 5 to 20 .mu.m.
Functions and Effects of Crystal Resonator Device of First
Embodiment
[0120] As described above, in the crystal resonator plate 2
according to this embodiment, the respective holding parts 22 are
protruded from the respective corner parts 21a of the vibrating
part 21 in the Z' direction of the AT-cut crystal so as to be held
by the external frame part 23. Thus, unlike the conventional
crystal resonator plate, the vibrating part 21 is not held at the
central position of the vibrating part 21 in the X axis direction,
i.e. the position where the displacement of the piezoelectric
vibration is large. Therefore, when the crystal resonator plate 2
is piezoelectrically vibrated, it is possible to efficiently cause
the piezoelectric vibration.
[0121] Also, the vibrating part 21 of the crystal resonator plate 2
is held by the external frame part 23 via the holding parts 22
respectively extended from the two corner parts 21a in the Z' axis
direction. Thus, the vibrating part 21 can be reliably held.
Furthermore, the respective wiring patterns of the first excitation
electrode 211 and the second excitation electrode 212 that are
formed respectively on both main surfaces of the crystal resonator
plate 2 can be independently disposed via the respective holding
parts 22 protruded from the two corner parts 21a. Thus, it is
possible to suppress the parasitic capacitance between the wiring
patterns, which prevents reduction in the frequency variation
amount.
Configuration of Variation of Crystal Resonator Device of First
Embodiment
[0122] Next, the respective configurations of the four variations
of the crystal resonator device in the first embodiment are
described with reference to FIGS. 9 to 13. Since these variations
merely differ from the above embodiment in formation of a groove m
in the above-described crystal resonator plate 2, only such a
difference is described hereinafter. The same components are
referred to as the same reference numerals and the description
thereof is omitted.
[0123] Also, any configuration obtained by combining Variation 1 to
Variation 4 may be provided.
Crystal Resonator Plate
[0124] The crystal resonator plate 2 according to these variations
includes a groove m that is disposed in at least one of the
vibrating part 21 and the holding part 22. The groove m is inclined
toward the central part of the vibrating part 21 (i.e. the central
part C of the first excitation electrode 211 and the second
excitation electrode 212 in plan view) relative to the X axis
direction of the AT-cut crystal (see FIGS. 9 to 13).
<First Variation>
[0125] In the variation shown in FIG. 9, the groove m is formed
from the corner part of the bottom of the mesa structure 213 toward
the holding part 22. In this variation, the groove m is provided so
as to make contact with the corner part 21a, thus it is possible to
efficiently suppress the leakage of the piezoelectric vibration.
However, the groove m may be formed so as to not make contact with
the corner part 21a. Also, the groove m may be formed so as to
extend from the vibrating part 21 to the holding part 22.
<Second Variation>
[0126] In the variation shown in FIG. 10, the groove m is formed
from a side of the mesa structure 213 along the Z' axis toward the
edge of the external circumference of the vibrating part 21.
[0127] With the variations shown in FIGS. 9 and 10, it is possible
to effectively suppress the leakage of the piezoelectric vibration
that transmits in the Z' axis direction.
<Third Variation>
[0128] In the variation shown in FIG. 11, the groove m is formed
from a side of the mesa structure 213 along the X axis toward the
edge of the external circumference of the vibrating part 21.
[0129] With the variation shown in FIG. 11, it is possible to
effectively suppress the leakage of the piezoelectric vibration
that transmits in the X axis direction.
<Fourth Variation>
[0130] In the variation shown in FIGS. 12 and 13, the grooves m are
constituted by one or more first grooves m1 formed in the first
main surface of the vibrating part 21 and one or more second
grooves m2 formed in the second main surface of the vibrating part
21. The first groove(s) m1 and the second groove(s) m2 are
alternately arranged in the holding part 22, from the side of the
vibrating part 21 to the side of the external frame part 23.
[0131] In the examples shown in the drawings, two first grooves m 1
are formed. One of them is formed in the vibrating part 21 and the
other is formed in the holding part 22. Likewise, two second
grooves m2 (see FIG. 13) are formed. One of them is formed in the
vibrating part 21 and the other is formed in the holding part
22.
[0132] With the variation shown in FIG. 12, the first grooves m1
and the second grooves m2 are formed so as to extend from the side
of the vibrating part 21 of the holding part 22 to the side of the
external frame part 23 so that the first groove m 1 and the second
groove m2 are alternately arranged (see FIG. 13). Thus, it is
possible to improve the effect of confining the piezoelectric
vibration.
[0133] In this Variation, the first groove m 1 is provided so as to
make contact with the corner part 21a, thus it is possible to
efficiently suppress the leakage of the piezoelectric vibration.
However, the first groove m1 may be formed so as to not make
contact with the corner part 21a.
Configuration of Crystal Resonator Device of Second Embodiment
[0134] Next, the configuration of the crystal resonator device in
the second embodiment is described with reference to FIG. 14. Since
the second embodiment merely differs in the location and number of
the holding parts 22 of the crystal resonator plate 2, only such
differences are described hereinafter. The same components are
referred to as the same reference numerals and the description
thereof is omitted.
Crystal Resonator Plate
[0135] In this embodiment, the holding part 22 of the crystal
resonator plate 2 is protruded from one corner part 21a disposed in
the vibrating part 21 toward the external frame part 23.
[0136] In this case, the vibrating part 21 of the crystal resonator
plate is held by the external frame part 23 via the holding part 22
that is protruded from one corner part 21a toward the external
frame part 23. Since the number of the holding parts 22 is reduced,
it is possible to efficiently hold the vibrating part 21.
Configuration of Crystal Resonator Device of Third Embodiment
[0137] Next, the configuration of the crystal resonator device in
the third embodiment is described with reference to FIGS. 17 and
18. Since the third embodiment merely differs in the connecting
structure of the holding part 22 and the external frame part 23 of
the crystal resonator plate 2, only such a difference is described
hereinafter. The same components are referred to as the same
reference numerals and the description thereof is omitted.
[0138] In the crystal resonator device according to this embodiment
as shown in FIG. 17, the external frame part 23 of the crystal
resonator plate 2 is provided with a recessed part 23a around the
boundary with the holding part 22, the recessed part 23a being
thinner than the external frame part 23. FIG. 18(a) is a
perspective view showing the connecting structure of the holding
part 22 and the external frame part 23 when the external frame part
23 is provided with no recessed part 23a. FIGS. 18(b) and 18(c) are
perspective views each showing the connecting structure of the
holding part 22 and the external frame part 23 when the external
frame part 23 is provided with the recessed part 23a.
[0139] As shown in FIG. 18(b), the bottom surface of the recessed
part 23a may be formed so that it is the same surface as the
surface of the holding part 22 (i.e. so that there is no step
between the recessed part 23a and the holding part 22).
Alternatively, as shown in FIG. 18(c), the bottom surface of the
recessed part 23a may be formed so that there is a step between the
bottom surface of the recessed part 23a and the surface of the
holding part 22. The bottom surface of the recessed part 23a and
the surface of the holding part 22 are in parallel with the first
main surface 2a and the second main surface 2b of the crystal
resonator plate 2. FIGS. 18(b) and 18(c) exemplarily show the
configurations in which the recessed parts 23a are respectively
formed in both main surfaces of the crystal resonator plate 2.
However, the recessed part 23a may be formed in at least one of the
main surfaces of the crystal resonator plate 2. In this way, the
respective thicknesses of the external frame part 23, the recessed
part 23a and the holding part 22 have the relation represented by
the following expression: (thickness of external frame part
23)>(thickness of recessed part 23a).gtoreq.(thickness of
holding part 22).
[0140] Also, in FIGS. 17 and 18, the recessed part 23a has a fan
shape in plan view and the boundary between the recessed part 23a
and the part other than the recessed part 23a of the external frame
part 23 has a curvature. However, in the present invention, the
shape of the recessed part 23a in plan view is not particularly
limited. The recessed part 23a may have a rectangular shape as
shown in FIG. 19(a) or a trapezoidal shape as shown in FIG.
19(b).
Method for Manufacturing Crystal Resonator Device of Third
Embodiment
[0141] Next, a method for manufacturing the crystal resonator plate
2 of the crystal resonator device according to the third embodiment
is described. The method for manufacturing the crystal resonator
device in the third embodiment merely differs from the first
embodiment in etching processes for forming the vibrating part 21,
the holding part 22 and the external frame part 23 in the crystal
plate. Thus, only such etching processes are described. Note that
the following description is based on the configuration in which
the mesa structure 213 is formed on the center of the vibrating
part 21 (see FIG. 6A).
[0142] In order to make the crystal resonator plate 2 of this
embodiment, a rectangular-shaped crystal plate is subjected to
three etching processes (etching for forming an external form,
etching for forming a mesa and etching for frequency adjustment),
thus the vibrating part 21, the holding part 22 and the external
frame part 23 are formed.
[0143] FIG. 20 is a diagram showing the crystal plate. The upper
portion is a plan view showing the crystal plate after it is
subjected to the etching for forming an external form. The lower
portion is a cross-sectional view taken from line A-A of the upper
portion. In the etching for forming the external form, a cut-out
part k3 is formed in a rectangular-shaped crystal plate so as to
form the external form of the vibrating part 21, the holding part
22 and the external frame part 23.
[0144] FIGS. 21A and 21B are diagrams each showing the crystal
plate. In each diagram, the upper portion is a plan view showing
the crystal plate in FIG. 20 after it is subjected to the etching
for forming a mesa. The lower portion is a cross-sectional view
taken from line A-A of the upper portion. FIGS. 21A and 21B show
the crystal plates that are subjected to respective etchings using
different masks. That is, there is a difference in the etched
region.
[0145] The etching for forming a mesa is an etching process for
forming an external form of the mesa structure 213 on the center of
the vibrating part 21. The etching for forming the mesa is to etch
at least the region of the vibrating part 21 other than the mesa
structure 213 and the region of the holding part 22. In the crystal
plate shown in FIG. 21A, only the region of the vibrating part 21
(except the mesa structure 213) and the region of the holding part
22 are etched. In the crystal plate shown in FIG. 21B, the region
of the recessed part 23a is also etched in addition to the above
regions.
[0146] FIGS. 22A to 22C and 23 are diagrams showing the respective
crystal plates. In each diagram, the upper portion is a plan view
showing the crystal plate after it is subjected to the etching for
frequency adjustment. The lower portion is a cross-sectional view
taken from line A-A of the upper portion. In FIGS. 22A to 22C, what
is different is the state of the crystal plate before being
subjected to the etching for frequency adjustment, or a mask used
for etching.
[0147] The etching for frequency adjustment is an etching process
for adjusting the respective thicknesses of the vibrating part 21
and the holding part 22 so that the oscillation frequency of the
crystal resonator device is a predetermined value. The etching for
frequency adjustment is to etch at least the region of the
vibrating part 21 (i.e. entire region including the mesa structure
213) and the region of the holding part 22.
[0148] The crystal plate shown in FIG. 22A is formed by etching the
respective regions of the vibrating part 21, the holding part 22
and the recessed part 23a of the crystal plate shown in FIG. 21A,
or by etching the respective regions of the vibrating part 21 and
the holding part 22 of the crystal plate shown in FIG. 21B. That
is, in the crystal plate shown in FIG. 22A, the holding part 22 is
subjected to two etching processes (i.e. the etching for forming a
mesa and the etching for frequency adjustment) while the recessed
part 23a is subjected to one etching process (i.e. either of the
etching for forming a mesa or the etching for frequency
adjustment). Thus, the crystal resonator plate 2, which has a step
between the bottom surface of the recessed part 23a and the surface
of the holding part 22, is formed as shown in FIG. 18(c).
[0149] In FIGS. 21A, 21B and 22A to 22C, the etched depth by the
etching for forming a mesa and the etched depth by the etching for
frequency adjustment are substantially the same. However, if the
etched depths of these etchings differ from each other, the depth
of the recessed part 23a can be adjusted by choosing a suitable
etching process for forming the recessed part 23a.
[0150] The crystal plate shown in FIG. 22B is formed by etching the
respective regions of the vibrating part 21, the holding part 22
and the recessed part 23a of the crystal plate shown in FIG. 21B.
That is, in the crystal plate shown in FIG. 22B, both the holding
part 22 and the recessed part 23a are subjected to two etching
processes (i.e. etching for forming a mesa and etching for
frequency adjustment). Thus, the crystal resonator plate 2, in
which the bottom surface of the recessed part 23a is the same
surface as the surface of the holding part 22, is formed as shown
in FIG. 18(b).
[0151] The crystal plate shown in FIG. 23 is formed by etching the
respective regions of the vibrating part 21 and the holding part 22
of the crystal plate shown in FIG. 21A, and there is no recessed
part 23a in this crystal plate. That is, in order to obtain the
crystal pate having the recessed part 23a or not having the
recessed part 23a, it is sufficient to change the mask used for the
etching. The number of etching processes is not changed. For this
reason, in the crystal resonator device according to this
embodiment, it is possible to manufacture the crystal resonator
plate 2 having the recessed part 23a without subjecting it to any
additional manufacturing process.
Functions and Effects of Crystal Resonator Device of Third
Embodiment
[0152] In the case where the crystal resonator device to which the
present invention is applied has a configuration not having the
recessed part 23a in the external frame part 23 as shown in FIG.
18(a), stress may be concentrated on the stepped edge of the
connecting part of the external frame part 23 and the holding part
22 when an impact or the like acts on the crystal resonator device,
which may result in snap of the connecting part.
[0153] In contrast, in the configuration as shown in FIG. 18(b),
the external frame part 23 is provided with the recessed part 23a
so as to have no step at the connecting part of the external frame
part 23 and the holding part 22. Thus, it is possible to avoid the
stress concentration at the connecting part, which leads to
improvement in shock resistance of the crystal resonator
device.
[0154] Also, in the configuration as shown in FIG. 18(c), the step
remains at the connecting part of the external frame part 23 and
the holding part 22. However, since the external frame part 23 is
provided with the recessed part 23a, the external frame part 23
itself also has a step at the boundary between the region where the
recessed part 23a is formed and the other region (hereinafter
referred to as "recessed part edge"). In this way, when an impact
or the like acts on the crystal resonator device, the stress is
distributed to the above two step parts. As a result, it is
possible to relax the stress concentration at the connecting part
of the external frame part 23 and the holding part 22, which leads
to improvement in shock resistance of the crystal resonator
device.
[0155] Apart from the improvement in shock resistance of the
crystal resonator device, in the configuration in which the
external frame part 23 is provided with the recessed part 23a, it
can be expected that vibration leakage from the vibrating part 21
to the external frame part 23 is suppressed. It is ideal that the
piezoelectric vibration is confined in the vibrating part 21,
however, it is difficult to completely confine the vibration.
Actually, the vibration leaks to the external frame part 23 to some
extent. Especially, in the configuration described in this
embodiment, the vibration leakage exerts a marked influence because
the vibrating part 21, the holding part 22 and the external frame
part 23 are integrally formed as the crystal plate. Specifically,
the vibration that leaks from the vibrating part 21 may pass
through the holding part 22 to reach the external frame part 23.
However, if the recessed part 23a is disposed in the position where
the vibration leaks from the holding part 22 to the external frame
part 23, it is possible to adjust the vibration leakage to prevent
resonance with the frame body, thus the vibration is not likely to
be transmitted to the external frame part 23.
[0156] In particular, in the configuration of the present
invention, the holding part 22 is protruded from the vibrating part
21 in the Z' direction, as described in the first embodiment. This
is a configuration in which the holding part 22 is protruded in the
direction perpendicular to the displacement direction of the
vibration of the AT-cut crystal resonator, so that the vibration
leakage is prevented. Ideally, the vibration of the AT-cut crystal
resonator is confined in the vibrating part 21. However, actually,
the vibration leaks to some extent as a secondary vibration that is
another vibration mode, and the holding part 22 protruding in the
Z' direction is likely to transmit the above vibration leakage to
the external frame part 23, which causes CI variation or frequency
variation. For this reason, the recessed part 23a is disposed,
which suppresses the vibration leakage to the external frame part
23. Thus, it is possible to obtain further stable
characteristics.
[0157] Hereinafter, other preferable examples of the crystal
resonator device according to this embodiment will be described.
For example, the width D1 of the recessed part 23a is preferably
larger than the width D2 of the holding part 22 (see FIG. 17).
Here, the width direction means the direction orthogonal to the
protruding direction of the holding part 22 from the external frame
part 23 in plan view. The reasons why the above configuration is
preferable are described below.
[0158] First, from the viewpoint of stress relaxation, when the
holding part 22 is flexed by vibration of the vibrating part 21
caused by an impact or the like on the crystal resonator device,
the recessed part edge of the recessed part 23a serves as the
stress concentration point. As the recessed part edge is spaced
apart from the vibrating part 21, the piezoelectric vibration is
not likely to be affected. Also, as the recessed part edge becomes
longer, the effect of the stress distribution becomes higher. Thus,
the configuration in which the width D1 of the recessed part 23a is
larger than the width D2 of the holding part 22 leads to the longer
recessed part edge, accordingly, the effect of the stress
distribution caused by the recessed part 23a is improved. Second,
from the viewpoint of vibration leakage suppression, the larger the
recessed part 23a becomes, the higher the effect of vibration
damping becomes. Thus, it can be expected that the vibration
leakage to the external frame part 23 is further suppressed and
that the CI value is further reduced or its variation is further
suppressed.
[0159] Also, as the shape of the recessed part edge of the recessed
part 23a, an arc shape as shown in FIG. 17 is preferable compared
to the rectangular shape and the trapezoidal shape as shown in
FIGS. 19(a) and 19(b). In other words, the shape of the recessed
part edge is preferably a shape having a curvature. When the
recessed part edge is formed so as to have a curvature, the
recessed part edge can have a shape with no vertex in plan view.
Thus, it is possible to avoid the stress concentration on the
vertex.
[0160] Also, on the above description, the recessed part 23a is
exemplarily shown in the configuration in which the vibrating part
21 of the crystal resonator plate is held by one holding part 22
(i.e. in the configuration of the second embodiment). However, the
present invention is not limited thereto. The recessed part(s) 23a
may be formed in the configuration in which the vibrating part 21
of the crystal resonator plate is held by two holding parts 22
(i.e. in the configuration of the first embodiment). Note that, in
the configuration of the second embodiment, the shock resistance is
lower than that of the first embodiment because of the smaller
number of the holding parts 22. For this reason, the configuration
of the third embodiment is preferably applied to the configuration
of the second embodiment, thus the shock resistance is improved by
forming the recessed part 23a.
[0161] As the foregoing embodiments and examples of the present
invention are to be considered in all respects as illustrative, it
is to be understood that such embodiments and examples are not
intended to limit the technical scope of the present invention.
[0162] In the above embodiments, a crystal resonator is used for
the crystal resonator device. However, the present invention can be
applied to a crystal resonator device (e.g. crystal oscillator)
other than that using the crystal resonator.
DESCRIPTION OF REFERENCE NUMERALS
[0163] 1 Crystal resonator device [0164] 11 Bonding material [0165]
12 Package [0166] 13 Internal space [0167] 2 Crystal resonator
plate [0168] 2a First main surface [0169] 2b Second main surface
[0170] 21 Vibrating part [0171] 21a Corner part [0172] 22 Holding
part [0173] 23 External frame part [0174] 23a Recessed part [0175]
211 First excitation electrode [0176] 212 Second excitation
electrode [0177] 213 Mesa structure [0178] 214 First extraction
electrode [0179] 215 Second extraction electrode [0180] 216
Resonator-plate-side first bonding pattern [0181] 217
Resonator-plate-side second bonding pattern [0182] k1 Inversed
U-shaped part in plan view [0183] k2 Oblong rectangular part in
plan view [0184] 3 First sealing member [0185] 3a First main
surface of first sealing member [0186] 3b Second main surface of
first sealing member [0187] 31 Sealing-member-side first bonding
pattern [0188] 4 Second sealing member [0189] 41
Sealing-member-side second bonding pattern [0190] 42a First
external electrode terminal [0191] 42b Second external electrode
terminal [0192] h1 First through hole [0193] h2 Second through hole
[0194] h3 Third through hole [0195] C Central part [0196] m Groove
[0197] m1 First groove [0198] m2 Second groove
* * * * *